Hydrophilic plant growth substrate, comprising a furan resin

ABSTRACT

PCT No. PCT/EP96/03847 Sec. 371 Date Jun. 11, 1998 Sec. 102(e) Date Jun. 11, 1998 PCT Filed Aug. 30, 1996 PCT Pub. No. WO97/07664 PCT Pub. Date Mar. 6, 1997The invention relates to a plant growth substrate, comprising a coherent, hydrophilic matrix of mineral wool fibres mutually connected via binder based on furan resin, and to use of a coherent, hydrophilic matrix of mineral wool fibres mutually connected via binder based on furan resin, as a plant growth substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydrophilic plant growth substrate,more in particular to a substrate based on a coherent matrix of mineralwool which is hydrophilic due to he use of a specific cured resin.

2. Background of the Invention

Plant growth substrates may have the form of plugs accommodated in atray hole, of cubes having a foil around the standing side surfaces, orof plastic wrapped slabs.

The currently used plant growth substrates which are based on a coherentmatrix of mineral wool use as a cured binder generally aphenol-formaldehyde resin. Due to the use of this type of binder, thematrix of mineral wool has to be provided with a so-called wetting agentin order to impart the substrate with hydrophilic properties. That is,the matrix can adsorb in a relatively short time period up to saturationamounts of water.

Although these types of known plant growth substrates are widely used,there is constant research to improve plant growth substrates, inparticular the phytotoxicity of the chemicals used. This phytotoxicitymay result for instance from the used wetting agent, or due to thebinder.

SUMMARY OF THE INVENTION

Accordingly the present invention relates to plant growth substratescomprising a coherent, hydrophilic matrix of mineral wool fibersmutually connected via binder based on furan resin, and to the use ofproducts produced by using a furan resin, for the culture of plants.

The plant growth substrates according to the invention comprise acoherent matrix of mineral wool. As mineral wool may be used stone wool,glass wool and/or slag wool. These matrices are produced usingconventional production methods which only depend on the starting wool.

For the plant substrates according to the invention use may be made of acoherent matrix of mineral wool. Coherency is obtained by curing theapplied furan resin such that the mutual fibers are mechanicallyconnected, which connections are substantially water resistant. However,it is noted that the plant growth substrate may consist of a so-calledgranulate having the form of mineral wool flakes comprising a number offibers and having a size of 0.2-5 cm.

When the plant growth substrate according to the present invention iscured and formed into a coherent hydrophilic matrix, the (higherdensity) substrate may have a compression strength up to 50 kPa, such asa compression strength in the range of 10-45 Kpa.

Hydrophilic character means in the context of the present invention thatwater is absorbed to a substantial extent/amount which may be measuredin the so-called sinking test in water to which no surfactant is addedand in which no mechanical force is applied to the substrate. It isnoted that without the use of a wetting agent the plant growth substrateof the invention has good plant growth (hydrophilic) properties.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The furan resins that are used in the present invention are based on thepolymerization of at least a furan molecule having the general formula##STR1## In this general formula A and B are polymerizable groups. Dueto polymerization are formed dimer, oligomer and polymer molecules inwhich the furan ring structure is joined at least to one other furanstructure by the group A and/or B. Furthermore, the furan ring may beless unsaturated, that is, it may comprise only one or no carbon-carbondouble bond at the 2, 3 or 4-position in the ring structure.

The polymerizable groups A and B may be selected from hydrogen, C1-C10alkyl groups, polysubstituted vinyl radicals, polysubstituted aromaticgroups, ketones, anhydrides, polysubstituted furfuryl, hydroxyls,aldehydes, carboxylic acids, esters, amines, imines, alkynes, alkylhalides, aromatic halides, olefinic halides, ethers, thiols, sulfides,nitriles, nitro groups, sulfones, sulfonic acids, and mixtures thereof.

Accordingly, the repeating groups in the product obtained bypoymerization comprise furan, furfural, furfuryl alcohol,5-hydroxymethyl-2-furancarboxyaldehyde, 5-methyl-2-furancarboxyaldehyde,2-vinyl furoate, 5-methyl-2-vinylfuroate; 5-tertbutyl-2-vinyl furoate,2-furfurylmethacrylate, 2-furfuryl methylmethacrylate, 2-vinyl furan,5-methyl-2-vinyl furan, 2-(2-propylene) furan (or 2-methyl vinylidenefuran), 5-methyl-2-methyl vinylidenefuran; furfurylidene aceton,5-methyl-2-furfurylidene, aceton, 2-vinyl tetrahydrofuran, 2-furyloxirane, 5-methyl-2-furyloxirane, furfuryl vinyl ether, 5-methyl-furfuryl vinyl ether, vinyl 2-furyl ketonebis-2,5-carboxyaldehyde furan, bis-2, 5-hydroxymethyl furan,5-hydroxymethyl-2-ethyl furanacrylate, 2,5-furandicarboxylic acid,2,5-furan diacid dichloride, 2,5-furan dicarboxylic acid dimethyl ester,2,5-furan methylamine, 5-carboxy-2-furan amine, 5-methylester-2-furanamine, bis-(2,5-methylene isocyanate) furan, bis(2,5-isocyanate) furan,2-isocyanate furyl, and 2-methylene isocyanate furyl.

The furan resins may be used as a concentrate or in diluted form in asuitable solvent, such as water. The solid content in a furan resincomposition when injected may be as little as 1 wt. %, generally lessthan 40 wt %, preferably 2-30 wt %, more preferably 5-20 wt %. Asuitable furan resin binder is a Farez M (TM) type from QO-Chemicals.Due to the use of these furan resins the plant growth substrate has anexcellent brownish colour. The density of the substrate is about 10-150kg/m³, such as 40-120 kg/m³.

The furan resin may be formed by polymerization, such as polyadditionpolymerization and condensation polymerization. These polymerizationsare known in the art.

In order to reduce the viscosity of the polymerization preparation to beused a co-solvent may be used. Suitable co-solvents are organic mono-,di- and polyacids, such as levulinic acid and maleic acid. Co-solventsmay be used in an amount up to 15 wt %, such as 2-10 wt % or generally4-8 wt %.

In order to cure a furan resin, the furan resin composition may comprisea catalyst. Examples are inorganic and organic acids, such ashydrochloric acid and maleic acid. Other catalyst examples areFriedel-Crafts catalysts, such as aluminum chloride. Other examples aresalts of inorganic and organic acids such as ammonium sulfate, ammoniumnitrate and urea salt of toluene sulfonic acid. Depending on the type ofcatalyst there may be used up to 20 wt %, generally in the range of 1-15wt %, such as preferably 8-10 wt %.

In order to improve the cohesion for binding to the fiber surface orfiber material a coupling agent may be included. Examples of couplingagents are silanes or organotitanates and oganozirconates. Examples ofsuitable silane coupling agents areN-Methyl-3-aminopropyl-trimethoxysilane and3-aminopropyl-triethoxysilane.

Furthermore, surfactants and extenders may be used in the furan resincomposition.

In order to avoid dust formation during plant substrate production andhandling a mineral, hydrophobic oil may be added, but the formedsubstrate maintains its hydrophilic properties.

Instead of using only furan-like molecules in the polymerizationreaction, copolymerizations may be used as well, in which other monomersare used, such as formaldehyde and phenol. By using these co-monomersthe hydrophilic properties of the resin may be adapted in the desiredsense. Formaldehyde and phenol may be used in more amounts up to 50%,generally in an amount of 1-45%, such as 2-30%, preferably 5-10%.Accordingly, due to the use of those monomers the hydrophilic charactermay be adjusted in the desired sense. However, when including othermonomers in the binder composition, formaldehyde is a preferred monomer.

When using formaldehyde as a co-monomer, it is preferred to include inthe furan resin composition a formaldehyde scavenger, such as ammonia orurea. Dependant on the amount of formaldehyde used ammonia and/or ureamay be present in amounts up to about 5 wt %, such as 0.1-3 wt %, inparticular 0.5-2 wt %.

Preferred is a furan resin based on furfurylalcohol and comprising aminor amount of formaldehyde, catalysts, formaldehyde scavengers andcoupling agent.

This furan resin composition is used and applied to stone wool fibresafter their formation while airborne. Furan resin is applied in such anamount that the resin content of the plant growth substrate is about1-10 wt % , such as 1.5-5wt % in particular 2-3.5 wt %.

It is noted that even if during the production of the plant growthsubstrate according to the invention 0.2-0.5% impregnating oil is usedwater absorption does not changed and is still up to about 100%.Hereafter Table 1 gives properties of the plant growth substratesaccording to the patent invention based on a furan resin, in particulara furfurylalcohol resin.

                  TABLE 1                                                         ______________________________________                                        Density          100    kg/m.sup.3                                                                            45    kg/m.sup.3                              Resin content    3.1    wt %    2.9   wt %                                    Compression strength                                                                           43     kPa                                                   Aged compression strength                                                                      36     kPa                                                   Delamination strength                                                                          11.5   kPa                                                   Swelling         2.5%                                                         Water absorption 100    vol %   100   vol %                                   Tensile strength                15.5  kPa                                     ______________________________________                                    

The following examples show the suitability of the hydrophilic plantgrowth substrates according to the invention, which comprise the furanresin binder. It is emphasized that the furan resin binder basedsubstrates according to the invention do not contain a wetting agent. Tothe contrary the conventional phenolic resin based substrates forcomparison purposes in the example do contain traditional wettingagents. These examples are given for the purpose of illustrating theinvention and not intended to limit the scope of the invention thereto.

EXAMPLE 1

The plant growth substrate was conventionally produced in a density of45 and 100 kg/m³ and used for plant growth (furan resin content about 3wt %). Cucumber plants were grown on these substrates and resulted inplants growing and yielding cucumbers similar to plants grown on plantgrow substrates based on phenol-formaldehyde resin and a wetting agent.

EXAMPLE 2

Similar growth substrates of the invention as used in example 1 (furthercomprising 0.5% impregnating oil) were used for growing garden-cress(common nutrient solution; EC=1, pH 6.7). In comparison to a standardgrowth substrate or granulate no growth differences have been noted upto after eight days. In a toxicity test no growth differences wereobserved after eight days.

EXAMPLE 3

Standard size growth blocks of the invention with furan resin as binderwere tested in propagation trials set up in a greenhouse. The growthblocks contained 2 wt % furan resin and during its production no mineraloil was added. Because the hydrophilic properties of the growth blocksare essential, the sinking times of the blocks were measured during theproduction and excellent sinking times of only 8-12 seconds wereobtained. Tomatoes and d cucumbers were tested and the results werecompared with growth blocks made of the same mineral wool but withphenolic resin as binder.

For tomatoes, 13 days after sowing the tomato plants were planted in thegrowth blocks and the results were collected 23 days after sowing.

For cucumber, sowing took place after saturation and the results werecollected 22 days after sowing.

The plant growth results (fresh weight [g/plant]) are as follows. Tomatoplants 136.2 g/plant; and 116.2 g/plant for furan resin and phenolicresin, respectively.

For cucumbers the growth blocks comprising furan resin provided 82.3gram per plant a phenolic resin growth blocks provided 81.5 gram perplant.

EXAMPLE 4

Full scale growth trials in slabs at growers with cucumber, tomato andsweet pepper gave results from propagation tests as shown in Table 2.The slabs contained 2-3.3 wt % binder and the result is given for thegrowth substrate with furan resin as % of growth substrate with phenolicresin.

                  TABLE 2                                                         ______________________________________                                               CUCUMBER  TOMATO      SWEET PEPPER                                     ______________________________________                                        Plant height                                                                           15 days: 99%                                                                              14 days: 110%                                                                             20 days: 99%                                          22 days: 100%                                                                             20 days: 113%                                                                             28 days: 104%                                Fresh weight                                                                           15 days: 105%                                                                             14 days: 105%                                                                             20 days: 102%                                         22 days: 101%                                                                             20 days: 109%                                                                             28 days: 97%                                 ______________________________________                                    

EXAMPLE 5

Full scale growth trials at growers with cucumber, tomato and sweetpepper gave the following conclusions evaluated after 4 to 6 monthsafter planting date. No significant difference was observed furan resinbonded slabs compared with phenolic resin bonded slabs for penetrationresistance, pH, water content and electrical conductivity. The furanresin bonded material has better rooting from the start, a slightlyearlier forming of crop fruits and better slab strength.

We claim:
 1. Plant growth substrate, comprising a coherent, hydrophilicmatrix of mineral wool fibres mutually connected via binder based onfuran resin.
 2. Substrate as claimed in claim 1, wherein the furan resinis obtained by polymerization of at least a furan molecule having thegeneral formula ##STR2## and/or its less unsaturated analogues, whereinA and B are each a polymerizable group.
 3. Substrate as claimed in claim2, wherein A and B are independently selected from the group comprisinghydrogen, C1-C10 alkyl groups, polysubstituted vinyl radicals,polysubstituted aromatic groups, ketones, anhydrides, polysubstitutedfurfuryl, hydroxyls, aldehydes, carboxylic acids, esters, amines,imines, alkynes, alkyl halides, aromatic halides, olefinic halides,ethers, thiols, sulfides, nitriles, nitro groups, sulfones, sulfonicacids, and mixtures thereof.
 4. Substrate according to claim 2, whereinthe furan molecule is furfurylalcohol.
 5. Substrate a claimed in claim1, wherein the furan resin comprises a co-solvent.
 6. Substrateaccording to claim 1, wherein the furan resin comprises a polymerizationcatalyst.
 7. Substrate according to claim 1, wherein the furan resincomprises a coupling agent.
 8. Substrate according to claim 1, whereinthe furan resin contains at least one substance selected from the groupconsisting of a surfactant, a coloring agent and an extender. 9.Substrate according to claim 1, wherein the furan resin is obtained bycopolymerization.
 10. Substrate according to claim 1, wherein thepolymerization comprises further formaldehyde and/or phenol. 11.Substrate according to claim 10, wherein the furan resin comprises aformaldehyde scavenge.
 12. Substrate according to claim 1, having adensity of 15-150 kg/m³.
 13. Substrate according to claim 1, wherein thebinder is cured.
 14. A method of preparing a plant growth substratecomprising the steps of admixing a quantity of mineral wool fibres witha furan-resin based binder to create a coherent, hydrophilic matrix ofmineral wool fibres mutually connected via said binder.
 15. The methodaccording to claim 14 further comprising the final step of curing theadmixed mineral wool fibres and furan-resin based binder subsequent totheir admixture.